1. Field of the Invention
The invention relates to novel curing agents for epoxy resins, to a process for making same and to an epoxy resin curing process using such agents characterized by a faster curing speed and improved physical properties of the finished resin as compared with prior art polyoxyalkylenepolyamine curing agents.
2. Description of the Prior Art
In U.S. Pat. No. 4,115,361 polyoxyalkylenepolyamines are used as a curing agent for vicinal epoxy resin and give it good color and low viscosity. However, they may require an accelerator to speed the amine cure of the epoxy resin, especially when below room temperature.
In addition to the use of accelerators, there have been suggested a method for mixing an amine compound of high curing rate with polyoxyalkylenepolyamine and a method for providing a higher curing rate by forming an addition reaction product of formaldehyde and phenol to polyoxyalkylenepolyamine. The usual result of these attempts is that the color of the resin deteriorates and the viscosity of the curing mass becomes extremely high.
Accordingly, the main object of this invention is to provide a higher curing rate to vicinal epoxy resins. It was found that this can be accomplished without addition of accelerators or of amine compounds of higher curing rate by curing with the addition-reaction product of an alkyleneimine to an polyoxyalkylenepolyamine. In addition, it was found that the physical property of the cured resin is improved.
A method using some of alkyleneimine derivatives as curing agents for epoxy resins or as a cross-linking agent is already known and reported in British publication, "High Polymer" 24,313 (1972), and Japanese publication "Petroleum and Petrochemistry" 15 (7), 118 (1971). The reaction of alkyleneimine with polyoxyalkylenepolyamine as in this invention to form an agent capable of providing a higher curing rate for epoxy resin was never reported.